Atm Device, Subscriber System, Communication System and Backup Method

1. An asynchronous transfer mode (ATM) device for carrying out communications with an opposite device by using a virtual communication channel on an ATM network provided by a virtual path/virtual channel (VP/VC) fixedly set based on a permanent virtual channel (PVC), comprising: setting means for setting a communication path on a non-ATM network so as to connect with said opposite device, the communication path being used for backing up said virtual communication channel; deciding means for considering said communication path as a transmission path for an ATM cell when failure occurs in said virtual communication channel, and then deciding a channel characteristic of a backup virtual communication channel set on said communication path by negotiating with said opposite device through said communication path; and switching means for switching a communication channel to be used for communications with said opposite device from said failed virtual communication channel to the backup virtual communication channel on said communication path having the channel characteristic decided by said deciding means when the failure occurs in said virtual communication channel.

2. The ATM device according to claim 1 , wherein said channel characteristic includes at least one selected from a virtual path identifier/virtual channel identifier (VPI/VCI) of said backup virtual communication channel, a band of said backup virtual communication channel, and a service class of said virtual communication channel.

3. The ATM device according to claim 1 , wherein said deciding means negotiates with said opposite device so as to make a channel characteristic of said backup virtual communication channel acceptable to said ATM device when the channel characteristic of said backup virtual communication channel requested by said opposite device is unacceptable in said negotiation.

4. The ATM device according to claim 1 , wherein said ATM device is an ATM multiplexer for relaying data received from a terminal housed therein to said ATM network.

5. The ATM device as an ATM multiplexer according to claim 4 , wherein for each connected terminal, said deciding means negotiates with said opposite device with which communications are carried out by using said virtual communication channel, the failure having occurred therein, when the failure occurs in the virtual communication channel used for communications by said terminal to decide a channel characteristic of the backup virtual communication channel, and for each connected terminal, said switching means switches a communication channel connecting with said opposite device with which communications are carried out by using said virtual communication channel, the failure having occurred therein, from said failed virtual communication channel to the backup virtual communication channel on said communication path, the backup virtual communication channel having the channel characteristic decided by said deciding means through negotiation with said opposite device when failure occurs in said virtual communication channel used for communications by said terminal.

6. The ATM device according to claim 1 , wherein said ATM device is an ATM switch.

7. The ATM device according to claim 1 , wherein said non-ATM network is an integrated service digital network (ISDN).

8. A subscriber system of an asynchronous transfer mode (ATM) network, comprising: an ATM device according to claim 4 ; and at least one terminal housed in said ATM device.

9. A communication system comprising: at least one subscriber system according to claim 8 ; an ATM network; and a non-ATM network.

10. A backup method for backing up a virtual communication channel on an asynchronous transfer mode (ATM) network provided by a virtual path/virtual channel (VP/VC) fixedly set based on a permanent virtual channel (PVC) by using a communication path on a non-ATM network, comprising the steps of: setting the communication path on said non-ATM network used for backing up said virtual communication channel so as to be connect with an opposite device, with which communications are carried out by using said virtual communication channel; considering said communication path as a transmission path for an ATM cell when failure occurs in said virtual communication channel, and then deciding a channel characteristic of the backup virtual communication channel by negotiating with said opposite device through said communication path, the backup virtual communication channel being set on said communication path; and switching a communication channel connecting with said opposite device from said failed virtual communication channel to the backup virtual communication channel on said communication path, the backup virtual communication channel having the channel characteristic decided through the negotiation with said opposite device when failure occurs in said virtual communication channel.